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Frilled shark

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The frilled shark is a unique predator found in the deep reaches of the ocean.

Chlamydoselachus anguineus NOOA
Chlamydoselachus anguineus NOOA

It belongs to the family Chlamydoselachidae, which includes two living species. One species is Chlamydoselachus anguineus, and the other is the southern African frilled shark, Chlamydoselachus africana. These sharks are often called "living fossils." This is because they possess primitive physical traits that have remained largely unchanged for millions of years. Their appearance and anatomy provide a direct link to ancient marine life.

Chlamydoselachus anguineus head
Chlamydoselachus anguineus head

The shark's body is shaped like an eel, a trait known as anguilliform. This long, dark-brown or grey body features fins located near the tail end. These include the dorsal, pelvic, and anal fins. The shark gets its common name from the appearance of its throat. It has six pairs of gill slits with extended filaments. These filaments create a fleshy, fringed look around the neck.

Frilled shark throat
Frilled shark throat

The shark's jaw structure is also very primitive. It uses amphistyly, which means the jaws attach directly to the cranium behind the eyes. This allows the shark to open its mouth very wide. Such a wide opening helps it swallow prey much larger than its own body.

To survive in the deep sea, the frilled shark uses a specific hunting strategy. It eats bony fish, smaller sharks, and cephalopods, which are soft-bodied animals like squid. To find food, the shark practices diel vertical migration. This means it stays near the ocean floor during the day. At night, it swims up toward the ocean surface to feed.

Chlamydoselachus anguineus (mouth and teeth) by OpenCage
Chlamydoselachus anguineus (mouth and teeth) by OpenCage

When it finds prey, it uses its eel-like movement to strike. The shark can curl its tail against a rock to lunge forward. Its mouth is filled with 300 needle-like teeth. These teeth are trident-shaped, meaning each has one main cusp and two smaller cusplets.

Chlamydoselachus anguineus teeth - tokyosealifepark-2019-1-8
Chlamydoselachus anguineus teeth - tokyosealifepark-2019-1-8

Scientists have a long history of studying these mysterious creatures. The zoologist Ludwig Döderlein first identified and classified the species. However, he lost his research manuscript during his travels. In 1884, the zoologist Samuel Garman published the first formal taxonomy. He based his work on a 2-meter-long female shark from Sagami Bay, Japan. Garman named the species Chlamydoselachus anguineus, which translates to "eel-like shark with frills."

Chlamydoselachus anguineus by garman
Chlamydoselachus anguineus by garman

His research helped establish the shark's place in the scientific world.

There has been much debate about where the frilled shark fits on the evolutionary tree. Garman believed it was related to the cladodont sharks from the Devonian period. Other scientists, like Theodore Gill and Edward Drinker Cope, suggested different connections. They thought the shark might be related to the Hybodontiformes, which dominated the Mesozoic era. Modern genetic analysis from 2016 suggests the shark may belong to the order Hexanchiformes. This order includes modern sharks and rays, such as the cow shark. Despite these debates, the shark's anatomy remains a subject of intense study.

The frilled shark lives in specific parts of the Atlantic and Pacific oceans.

Chlamydoselachus anguineus distmap
Chlamydoselachus anguineus distmap

They prefer the outer continental shelf and the upper continental slope. They often stay near biologically productive areas where food is plentiful. In Suruga Bay, Japan, they are commonly found at depths between 200 and 600 meters. They can be caught at depths of 1,000 meters, but they are rare below that. The sharks are usually solitary, though large groups have been seen near underwater seamounts. These seamounts may serve as important locations for mating.

Reproduction in frilled sharks is a slow and complex process. They are aplacental viviparous, meaning the young develop inside the mother without a placenta. Instead, the embryos grow inside egg capsules within the mother's uterus. When the pups are born, they feed on yolk. The gestation period, or the time the mother carries the young, can last up to 3.5 years. A single litter usually consists of 2 to 15 pups. This slow reproduction rate is a significant part of their life history.

Understanding the frilled shark helps scientists learn about the history of Earth. The species has existed since the Late Cretaceous and Late Jurassic epochs. This means they have survived through massive changes in the planet's oceans. While they are sometimes caught as bycatch in commercial fishing, they remain a vital part of the deep-sea ecosystem. They serve as a living window into the ancient, primeval seas.

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🖼️ Images & Media (8)
File:Chlamydoselachus anguineus head.jpg
Chlamydoselachus anguineus head.jpg
File:Chlamydoselachus anguineus by garman.png
Chlamydoselachus anguineus by garman.png
File:Chlamydoselachus anguineus NOOA.jpg
Chlamydoselachus anguineus NOOA.jpg
File:Chlamydoselachus anguineus distmap.png
Chlamydoselachus anguineus distmap.png
File:Chlamydoselachus anguineus (mouth and teeth) by OpenCage.jpg
Chlamydoselachus anguineus (mouth and...
File:Frilled shark throat.jpg
Frilled shark throat.jpg
File:Chlamydoselachus anguineus teeth - tokyosealifepark-2019-1-8.jpg
Chlamydoselachus anguineus teeth -...
File:Frilled shark head2.jpg
Frilled shark head2.jpg
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